Hi,

I obviously don't know the history of that machine, but if it were used in an actual industrial area, it is possible that a tech had soldered a wire somewhere that force the machine to turn on always. From one of the techies that I have worked with I have heard a story that they have constantly received a call from a 24/7 industrial installation that one of their computers shutdown randomly, and after having to go there a lot of times, they simply soldered a wire to set the machine to permanent "ON" status so they no longer get constant support calls from the plant.

MagefromAntares wrote on 2026-04-28, 18:45:

Hi,

I obviously don't know the history of that machine, but if it were used in an actual industrial area, it is possible that a tech had soldered a wire somewhere that force the machine to turn on always. From one of the techies that I have worked with I have heard a story that they have constantly received a call from a 24/7 industrial installation that one of their computers shutdown randomly, and after having to go there a lot of times, they simply soldered a wire to set the machine to permanent "ON" status so they no longer get constant support calls from the plant.

HA! Well. . . shit. That's a super valuable insight, and I think it means I should probably take it back apart to inspect things more carefully. Everything looked fine by initial inspection, but. . . who knows.

CN1 on the backplane board connects to the PS-ON pin on the ATX connector, it's meant to be connected to the motherboard with a cable.

PSON is likely connected directly to Ground on the backplane. There may be a jumper connecting them that you can remove, or there may be a wire soldered on the back of the card, but if you remove that connection you will need to connect 5VSB and PSON to the SBC somehow so it can power up in the ATX way

Well son of a. . .
Look at this little sneaky jerk.

Never thought to look inside a connector for a jumper.

Here's the pinout from each manual:

Thank you both for your replies. You're both right that once I pull this jumper, it doesn't come on automatically when the PSU is plugged in, and that I can't then turn it on.
Looking through both schematics/manuals/datasheets, I do see now where I need to hook this connector into on the Mobo. But that does mean I need a cable I don't have.

It looks like it's a standard 3pin fan header on one side, and a 3 pin JST connector on the other? I see the part number for the cable in one of the manuals (1700030500), and I do see one for sale on Ebay but they're asking $30 which is mighty steep for two little plastic connectors and a couple of wires.

Anyone know if this kind of wire is something more standard that I could buy for a few bucks using a non brand name/official part number?

So, maybe I can roll my own? I'm a computer guy, but admittedly my electrical/electronics knowledge is pretty limited. I think I've got a little box of JST connectors someplace, but I'd have to find the fan connector (not sure what it's called officially). It looks like the official part only has two wires, connecting the outer pins. That makes sense for PSON-PSON and presumably for 5v-VCCSB (though I don't know what SB is?). The center pins aren't used tho.

On the Backplane the center pin looks to be Ground, but on the Mobo it's Vcc, so I assume if those WERE connected it'd just short? So. . . 3 pin connectors, but only 2 wires? Does that sound right?

As soon as I post that and look at the photo again I realize that center pin is probably there just for that jumper.

Tumerboy wrote on Yesterday, 00:14:

So, maybe I can roll my own? I'm a computer guy, but admittedly my electrical/electronics knowledge is pretty limited. I think I've got a little box of JST connectors someplace, but I'd have to find the fan connector (not sure what it's called officially). It looks like the official part only has two wires, connecting the outer pins. That makes sense for PSON-PSON and presumably for 5v-VCCSB (though I don't know what SB is?). The center pins aren't used tho.

Yep, just connect the outer pins. SB is for "stand by", it's a 5V line that the PSU always outputs which is used to hold PS-ON high when power isn't required. So just remember 5VSB is "live" as long the PSU has mains power even if it's not "on".

If you're desperate and have a spare old PC case laying around, you can probably steal one of the front LED cables and clip it in half to make the plugs fit on the outside pins.

I used a CD-ROM audio cable before for this purpose because it had the correct connectors (that was for an Adlink backplane and SBC though which uses 5 pin 0.1" headers). you could also use 3x female to female jumper wires that are 0.1" pitch on one side and 2mm on the other side. Just be very careful that you have the pinout correct and don't short anything together that shouldn't be.

Well, you learn something new every day. I wanted to actually look it up this time instead of just state it's a JST style 3-Pin connector in 2.54.

JST-XH connector. Apparently 2.50mm even though all the generic seller listings read 2.54mm. https://en.wikipedia.org/wiki/JST_connector

Unless I'm completely mistaken. But that looks right.

I realized I'd replaced the CPU cooler on this (the old fan was making a racket) so I snipped the wires off that fan, and I found that I already had a little pot with a 3 pin JST connector on it in my bins, so I snipped that too. Should be able to splice them and have a working cable.

Unfortunately I then sliced my finger open and spend last night in the ER. So progress is slowed.

But thanks for all the help!

And yes, I also noted that JST connecters are 2.5mm not 2.54mm in my research yesterday.

You could go into DOS mode and shut the PSU by software if it is an ATX compliant PSU.

You could use my SANE program for that. It even supports APM and old style brute force power off, between other things:
SANE - DOS All-in-one "safe" shutdown, reboot, bios password reset and DOS stabilization utility.

Software isn't going to be able to do anything when the PS-ON line is jumpered to GND, as shown earlier in the thread.

You can flush buffers and caches to power the system off, without hoping for the best.

Success!

Here's my Frankensteined cable. (only spliced in one spot, the other shrink is just to keep it more cohesive)

I was able to get this plugged in at both ends, and after a momentary panic when it failed to post, and then reseating the mobo, it's working great! Power switch on the front will turn it on, and if held for a few seconds, back off. And once booted into Win98SE, Shutting down turns off the box.

Thanks for all the help, folks! Much appreciated!

Advise for others using these kind of boards. There are different pinouts for the power cable from different manufacturers. I once fried an advantech board using the wrong one in a non advantech backplane.

eisapc wrote on Today, 06:33:

Advise for others using these kind of boards. There are different pinouts for the power cable from different manufacturers. I once fried an advantech board using the wrong one in a non advantech backplane.

Oof. That’s rough.

Luckily I had the manuals with pinouts for both the mobo and the backplane, and better yet, both had the pins printed on the pcb.

But I certainly checked it about 18 times before plugging in power again.

If the pins aren't labelled (like they are on the above backplane photo) you'd definitely want to probe them to confirm what signals they are.